Among various biocides known, peroxycarboxylic acids are increasingly used as antimicrobials and bleaching agents in many applications, owing to their high efficacy against a broad spectrum of microorganisms, color safe property, low residues and nontoxic nature of their decomposition products. Peracetic acid is the most commonly used peroxycarboxylic acid and has been shown to be a good biocide, but only at relatively high concentrations (generally greater than 80 part per million). Similarly, peroxyfatty acids have also been shown to be biocidal, but only at high concentrations (greater than 200 ppm). In contrast, peroxyformic acid has an advantageous degree and range of microcidal properties compared to other peroxycarboxylic acids, such as peracetic and perproprionic acids, as disclosed by V. Merka et al in J. Hyg. Epidem, Microbiol. Immunol., 1965 (IX) 220, as well as in European Patent Application No. 863,098,96, which are incorporated herein by reference in their entirety.
Most often, peroxycarboxylic acids are generated in a chemical plant through an acid catalyzed equilibrium reaction, and then shipped to customers for on-site use. Due to the limited storage stability of peroxycarboxylic acids, the peroxycarboxylic acids must be packed in special containers and shipped under strict Department of Transportation (DOT) guidelines. Further, excess amounts of reagents (e.g., acids, oxidizing agents, and stabilizers) are present in these compositions during shipping to prevent decomposition. For certain peroxycarboxylic acids, such as peroxyformic acid, however, the inherent instability of the substance relative to the higher alkyl peracids, and the explosive nature of the substance at the concentrate make it an even more significant challenge to be manufactured, stored and transported before dilution prior to use, in the similar way like higher alkyl peracids. Accordingly, peroxycarboxylic acids have alternatively been generated in situ through a perhydrolysis reaction of the higher alkyl carboxylic acid esters of polyhydric alcohol under strong alkaline conditions (e.g. pH greater than 12) and thereafter acidified to become an efficient biocide, as disclosed in the Patent Application No. WO2012/090124 and U.S. Pat. No. 7,919,122, each of which are incorporated herein by reference in their entirety.
Such in situ generation of peroxycarboxylic acid biocides are thereafter suitable for use when a sufficient concentration biocide is achieved. However, certain assays for peroxycarboxylic acid compositions are destructive to the biocide concentration and therefore undesirable. For example, iodide is a destructive assay, as disclosed for example in U.S. Pat. No. 4,900,682. Moreover, other fluorescent tracers may be destructive to peracid compositions. Fluorometric spectroscopy concerns the detection of fluorescent light emitted by a sample and involves using a beam of light, usually ultraviolet (UV) light, that excites the electrons in molecules of certain compounds in the sample and causes them to emit light of a lower energy (i.e., to “fluoresce”). There are several types of fluorometers for measuring emitted fluorescence. Fluorometers generally have of a source of excitation radiant energy, an excitation wavelength selector, a sample cell to contain the sample material, an emission wavelength selector, a detector with signal processor and a readout device. Filter fluorometers use optical filters to isolate the incident light and fluorescent light. Spectrofluorometers use diffraction grating monochromators to isolate the incident light and fluorescent light. One method of monitoring the concentration of a chemical product (e.g., a cleaning agent) within a water sample relies on monitoring the fluorescence of the product that occurs when the sample (and the product within the sample) is exposed to a predetermined wavelength of light. Accordingly, the use of fluorescent actives often requires use of optical measuring devices. However it may be more desirable to have a built-in quantitative measurement system as opposed to requiring a device, such as controller modules or other handheld devices.
Accordingly, it is an objective of the invention to develop self-indicating systems for use with on-site generation of peroxycarboxylic acids to provide a visual indicator of peroxycarboxylic concentration without destroying the peroxycarboxylic acid, including for example peroxyformic acids. In a further aspect, the invention is suitable for providing a visual indicator that further provides a stabilizing effect on the peroxycarboxylic acid as opposed to a destructive effect.
A further object of the invention is to provide a method of indicating completion of a peroxycarboxylic acid generated by perhydrolysis in situ through a visual indication to a user, including a non-fluorescent marker or indicator, and a non-catalytic or destructive indicator.
It further is an object of this invention to provide for a quick visual screening procedure to screen and test toxicants and biocides useful in control of microorganism growth and provide for control or elimination of microorganism growth.
Other objects, advantages and features of the present invention will become apparent from the following specification taken in conjunction with the accompanying drawings.